Field of the Invention
This invention relates to a switch circuit which is arranged to be opened and closed by transmitting signals from switches to electronic switches such as analog switches or the like through a control circuit. More particularly, the present invention pertains to a switch circuit equipped with the function of setting up the initial condition of switches when main power is supplied.
Recently, there has been developed a switch circuit comprising an integral combination of push-button switches and a semiconductor integrated circuit for storing signals from the push-button switches and actuating electronic switches to control a signal source. Commonly, such push-button switches comprise self-restore type contacts and are paired with pilot lamps. The switch circuit includes a signal input stage which comprises an array of plural such switches, wherein when a given one of the switches is turned on, the remaining switches are turned off. The switch circuit also includes an auxiliary circuit which is arranged, when the main power supply is interrupted, to enable a storage circuit to hold the memory of a preset condition so that the latter is available when the main power supply is restored.
However, the foregoing conventional switch circuit is disadvantageous in that when main power is supplied or when interruption of the main power supply persists for a long time, there is the tendency that the memory at the storage circuit is cleared; if the main power is supplied under such a condition, an unspecific one of the switches tends to be turned on so that an unstable set condition occurs.